Bone marrow contains at least two kinds of stem cells, hematopoietic stem cells and stem cells for non-hematopoietic tissues (1–27) variously referred to as mesenchymal stem cells or marrow stromal cells (MSCs). MSCs are of interest because they are easily isolated from a small aspirate of bone marrow, they readily generate single-cell derived colonies (1, 2, 5, 18, 21, 25, 27), the single-cell derived colonies can be expanded through as many as 50 population doublings in about 10 weeks (25), and they can differentiate into osteoblasts, adipocytes, chondrocytes (1–13), myocytes (9), astrocytes, oligodendrocytes, and neurons (17, 23, 26, 27). For these reasons, the cells are currently being tested for their potential use in cell and gene therapy of a number of human diseases (22, 24).
There is a long felt need in the art for the generation of large numbers of homogeneous cells for use in alleviating disease in and of themselves, or as delivery vehicles for in gene therapy applications. The present invention satisfies these needs.